Insulating bushing for high tension conductors



March 22, 1932. 1,850

INSULATING BUSHING FOR HIGH TENSION CONDUCTORS A. N. Q QWDERET AL FiledJan. 2. 1929' Patented 22, 1932 UNITED STATES PATENT OFFICE ALEXANDER N.OBOWDEB, OF BO'UN'DBRQOK, NEW .TEBSEX, AN D AARON IN. SIMMONS, 01'TBENTON, IIOHIGAN, ASSIGNOBS TO RESEARCH CORPORATION, OF NEW YORK, H. Y

A ooarona'rlon or new You msomrme BUSHING FOR HIGH EENBION CONDUO'IOBSApplication filed January 8, 1929. Serial No. 829,747.

This invention relates to insulating bush-I ings particularly adaptedfor use in electrical precipitation.

In this type of device, suspended materials,

such as dust, fumes, mists, and the like are precipitated from a streamof gas in which they are suspended by passing the stream of gas throughan electrical field maintained between discharge electrodes andcollecting electrodes at a high difi'erence of potential (the welllfl'lOWIl Cottrell process). These electrodes are. usually mounted in achamonly does wasteful leakage of current occur over the uncleansurfaces, which prevents the maintenance of an efiectively highprecipitation voltage, but local discharges or arccvers occur over theirsuriaces, whichcause shattering of the insulators, with resultant damageto the high tension system which may cause the hending of high-tensionmembers, the breakin of other insulators and long down or units repairsare made.

According to invention, these difi culties are obviated by surroundingthe hightension lends at the places where they pass into theprecipitator chamher with bushmgs reeds or like material, which hecheaply made, quickiy replaced, and do porcelain, shatter when an arcover nose hushings can be made gas-tight, and thus, in some cases, thereis ohvia'ted the necessity of hoods or gas-tight insulator compartments.

'lfhe invention will be readily understood irom the accompanyingdrawingsin which E, is diagrammatic vertical section through the upper part ofone form of electrical precipitator;

.l ig 2 is a top view of the bushing and supporting bar for thehigh-tension conductor;

Fig, 3 is an elevation of one half ofthe insulator;

Fig. 4 is a plan view of Fig. 3;

Fig. 5 is an elevation of the other half of the insulator;

Fig. 6 is a plan view of a cover-piece; and

Fig. 7 is a side View of Fig. 6.

The bushing is made of gypsum, plaster of Paris, asbestos meal orcement; cement mixed with lime, Sil-o-cel, or magnesia; cementitiouscompoundscontaining wood or paper fiber; or the material @own on themarket as Gypsum wood pulp plaster, which is understood to be a mixtureor plaster of Paris, lime and wood fiber. All of these materials can heeasily molded when mixed with water and will set and at ordinarytemperatures, and when dry rave insulating qualities. All thesematerials may be characterized as self-setting in contradistinction toporcelain-like materials which have to be baked hi h temperatures.

Bushings made of t ess or like materials have the physical property thatthey do not shatter, as oes porcelain, when an arc-over takes placethrough the material or along its surface. These materials which containfibrous hinders, such as wood or asbestos fiber, have an increasedresistance to crac ing or pulling apart when the outer and innersurfaces or the bushing are subjected to vdi'Eerent temperatures,

The bushings are preferably made in two sections as shown in 3 to 7. Quehollow half section B has semi-cylindrical outer surface, has anintegrally formed cover portion H, provided with semi-circular openingl, and grooves F, in its edges. The corresponding halt section E isshown in Fig. 5. and is like section B, except that it is somewhatshorter and has a separate cover portion D, also provided with opening Iand grooves 1 sch of the sections is preferably provided on its interiorwith deep valleys or corrugations to give larger leakage surfaces. Thesevalleys may be omitted or may be located on the outside of the hushinprovided with a core to form the interior tense? In assemblin a layer ofabout one inch of cement, as shown at 0, Fig. 1, is spread 'on the topof the chamber and around the opening for the high-tension wire.Sections like Band E are then put into place and held together by anysuitable clamping rings M, shown in dotted lines in Fig. 1. The

' grooves F are then filled with a thin mixture of gypsum, and theclamps are drawn tight. After this, the top-piece D is cemented ontosection E, thus completing the bushing with the top sections closelysurrounding the high tension lead, and making a practically gastightjoint therewith. After the cement has set, these clamping rings areremoved. The cover section D can be removed at any time to inspect theinterior without disturbing the remainder of the bushing.

This new type of bushing therefore has the advantages that itconstitutes a relatively gas-tight closing means at the high tensioninlet points; does not crack under the temperature variationsencountered; after an arcover has occurred, does not form currentleakage paths; dissipates absorbed moisture rapidly enough to preventshort-circuit through the moisture; allows high tension discharge systemsupporting porcelain insulators to be located where they will notaccumulate moisture and fail mechanically from electrical -eakage;cheapens construction by eliminating insulator hoods and gas-tightcompartments; and reduces maintenance costs by reducing the frequency ofinsulator cleaning and replacing of broken insulators. The location ofthe bushings with respect to the high tension system for electricalprecipitators of the Cottrell type is shown in Fig. 1,

' in which J, J are porcelain insulators supporting a conducting bar K,from which are suspended the high tension leads N, N, passing throughthe bushings L, L, which surround openings in the top S of theprecipitator chamber. Supported by these leads N, N, is anotherconducting bar P, which in turn supports the discharge electrodes Q, Q,arran ed between collecting electrodes R, R, accor ing to commonpractice. '1 isa supplemental insulator compartment, which may beomitted. I

We claim;

1. Abushing for high tension electrical systems consisting of a hollowcylindrical structure and having openings at top and bottom for thehightension lead, the bushing comprising a plurality of sections composed ofa self-setting cementitious insulating material, said sections beingcemented together with similar cementitious material.

2. A bushing for high tension electrical systems composed of aself-setting cementitious insulating material, comprising a half sectionprovided with a cover-piece, another section without a cover-piece and ahalfcover piece mounted on said second section.

3. A bushing as claimed in claim 2 in which the abutting faces of thesections are provided witlh grooves filled with cementitious materia 4..A high tension electrical system comprising a porcelain insulator, ahigh tension conductor carried by said insulator, and a hollow bushinghaving a separable top portion surrounding said high tension conductor,said bushing being composed of a self-setting cementitious insulatingmaterial, the top portion being cemented to the remaining portion withsimilar cementitious material.

In testimony whereof, we afiix our signatures.

ALEXANDER N. CHOWDER. AARON N. SIMMONS.

